Rheostat.



Patented May 28, 1918.

N. D. LEVIN.

RHEOSTAT.

APPLICATION FILED AUGJI. 1915.

INVENTOR ATTORNEY UNITED STATES PATENT OFFICE.

.NILS D. LEVIN, OF COLUMBUS, OHIO, ASSIGNOR TO THE JEFFREY MANUFACTURING COMPANY, OF COLUMBUS, OHIO, A CORPORATION OF OHIO.

BHEOSTAT.

Specification of Letters Patent,

Patented May as, 1918.

Application and August 17, 1915. Serial in. 45,961.

.of indefinite number, the parts being so constructed and related that units can be added in a series one after another until a resistance of a predetermined degree is attained.

Much difliculty has been experienced, and but little success achieved, in providing artificial resistances for certain lines of electric motor apparatus; for example, such motors as are used in coal mine work.

In mines, and similar places, the room within which electric motors and their adjuncts must be contained is limited, and the space restricted. The diificulty referred to arises from the necessity of providing mechanical apparatus which can be frequently moved about, in the contracted space in the mine rooms, and which shall be composed of parts that will be as efiicient as possible in respect to the development of power, and which shall, at the same time, e durable and have suflicient strength.

Of the space available around such mine apparatus (as mining machines, electric locomotives, and the like) for their motors and their adjuncts, that part which can be allowed for such devices as rheostats is particularly restricted. Itis not only necessary to rovide rheostat or resistance mechanism whlch will be eflicient in the controlling of powerful currents, but which will allow rapid dissipation of heat, and have the parts so arranged that the radiating surfaces will be separated sufliciently to permit such dis sipation. 1

The object of the present invention is to provide a resistance device which will have all of its parts compactly arranged in restricted s ace and yet will be sufliciently strong an durable for the work to which it is subjected, which will insure perfect insulation at all times, will have the parts accessible for repair and renewal, will have the conducting elements exposed to permit free radiation of heat, can be initially made at minimum cost, and can be readily repaired at'points remote from the shops and without skilled labor. Y

Figure 1 is a front elevation of a resistance device embodying my improvements;

Fig. 2 is a section on the line 22 of Fig. 1;

.Fig. 3 is a side view of that part of the device which is shown in Fig. 1;

Fi 4 is a perspective of one of the insulating and conductor-holding boxes.

The resistance devices, proper, consist of v metallic strips 1 and 2. They are preferably formed by cutting sections from sheets or ribbons of metal of suitable length and composition. These sections are of the same width, and, as concerns their length, they are of two sets, all those of each set being of equal length. They are thin and flat, and hence rapidly dissipate heat, which quickly reaches the surfaces and escapes from the latter. Being relatively wide, they insure a conducting contact when one is placed against another.

They are arranged in layers one above an other, each layer comprising two of the strips 1 and two of those indicated at 2; the four parts of each layer being analogous to the four side arts of a square coil. When arranged as sliown the current passes first through one of the long strips 1, then through one of the short strips 2, then through the other long strip 1, and then through the second strip 2. The latter is, at its end, insulated from the initial strip 1 of its layer, but contacts with the strip 1 of the next layer. The end parts of the second layer are insulated from the cornersof the first layer and at its termination it is insulated from its initial strip 1 of its own layer. And so on throughout the series.

After enough of the layers have been superposed'to provide the predetermined deprotecting casing.

I have devised an improved insulating holder for such a resistance element, and have illustrated it in the drawings.

17 indicates a metallic box-like casing formed with the walls 4 and 5 and the intermediate side walls 3, these inclosing a chamher or a space which is open on the front and rear. Or the casing can be formed with two chambers or receiving spaces, in which case the wall 5 will be intermediate of two walls such as indicated at 4.

A suitable number of pedestals or lugs 6 are provided, preferably by casting them integral with the casing, which permit the fastening thereof to the motor or other part of the mechanism, and which are offset in such way as to provide an open space between the resistance element's andthe surface, indicated by the dotted line 6, of the part to which the casing is attached. At

4P flanges are formed on the casing'to serve as shoulders or seats.

In each of the chambers in the casing there are fitted two box-like retainers 7 of insulating material, such as porcelain. Each has a continuous back wall 18, continuous side walls 19, and inclosed or continuous end wall 12. The front wall is cut away, as shown at 20, the remaining parts of this wall constituting flanges, as at 8 and 10. On the back wall .18 opposite the central part of the opening 20 there is a rib 9 projecting somewhat forward from the wall 18. The parts 8, 10, 9, 18 and 19 are all preferably integral. There is no wall at the end of the box opposite to the closed wall 12.

It will be seen that at each side of this box-like retainer there are two partially inclosed chambers 21.

The distance between the plane of the side face of-the rib 9 and the plane of the edge face of the flange 8, or of the flange l0, is equal to the width of a resistance str p; and the distance from the plane of the outer edge of the rib 9 to the plane of the inner faces of the flanges 8 and 10 is also equal to the width of a strip.

Two of these boxes 7 are placed in the casing 17 with their openings 20 opposite to each other, one of the side walls 19 of each box abutting against a flange P on the casing After placing the two boxes in the casing one of the resistance structures above descrlbed can be put in place by having its ends inserted into the chambers in the boxes so as to be positioned substantially as shown in Fig. 3.

Or, the resistance element, as an entirety, can be built up, piece by piece, in the insulating boxes after the latter are set in the casing. In doing this two of the long strips 1,1 are dropped fiatwise through the open end of the boxes until they rest upon the insulating walls 12.

Then one of the shorter strips 2 is placed across their ends.

Then a square insulating strip or block 11 is placed upon the initial end of the first strip 1. Then a conductor strip 2 is laid with one end on the second conductor strip of the bottom layer, and with its other end upon the insulating piece 11. Then three of the Strips or squares 11 of insulation are placed in the chambers 21, at each of the three other corners of the layer, and another series of the strips 1 and 2 are put in position to form a second layer.

In this way, with alternating layers of conducting strips and insulation pieces, the resistance element is built up until the total length of the conductor provided by the strips is of the required length.

F or each resistance element the two strips 1 at the ends of the series are respectively -provided with terminal connectors 16.

After the pile has been completed outside insulating strips or plates 14 are placed upon the top of a pile, one at each end of the resistance element, and outside of these reinforcing or pressure plates 15 are placed.

Against the latter binding screws 13 havecarrying away the heat that comes to, and

radiates from, the surfaces of the strips.

There are no small connecting screws or similar parts for binding together the different elements of the resistance; the device is compact, and the parts cannot be rattled or shaken loose. As an entirety, the resistance occupies but small space. In case of damage any part can be readily withdrawn and a new one substituted without skilled labor or requiring work at the shops.

What I claim is:

1. The herein described resistance element composed of a series of insulated layers each layer comprising longitudinal strips and transverse strips arranged to leave projections at the ends of the longitudinal strips and having a freely separable engagement therewith, an insulating retainer arranged to engage with the transverse strips and with the projecting ends of the longitudinal strips" to prevent their displacement in relation to each other, and means for pressing the strips together.

2. In a rheostat, a resistance element having a series of insulated layers each layer nal strips, each strip having a freely separable engagement with adjacent strips, insulating retainers for the end parts of the element having chambers and flanges substantially as set forth to engage with the longitudinal strips and the transverse strips to prevent their lateral displacement in 'relation to each other, and means for pressing the strips together.

3. In a rheostat, the combination with a series of resistance strips arranged end to end to provide an electric circuit section, each strip being positioned to have its longitudinal lines transverse to the longitudinal lines of adjacent strips whereby the series of strips surrounds an insulating space, of insulating retainers having recesses wherein the ends of the strips are loosely fitted and by which the strips are held against lateral displacement, and means for pressing the stri s together on lines transverse to their wi er faces.

4. In a rheostat, the combination with a series of conducting strips arranged end to end to form a circuit section throughout the series and so disposed as to form two side sets of strips and two end sets, the four sets surrounding a parallel side chamber, and all of the strips of the end sets being 0 transverse to those of the side sets, insulating retainers which loosely engage the overlapping ends of the strips and hold them against lateral displacement, and clamping devices acting to hold all of the strips in predetermined position.

5. In a rheostat, the combination of a series of insulating layers of resistance separable engagement with each other, in-

sulating retainers for the ends of the strips and provided with means for preventing the strips from being displaced laterally, in relation to each other, and means-for pressing the strips together.

7 In a rheostat, the combination of a' series of flat elongated relatively thin resistance strips arranged to have their wider faces freely separably engage with each other, insulatin retaining devices engaging the edges 0 the end parts of the strips to secure them against lateral displacement, a casing surrounding said strips and retaining devices, and pressure devices for locking the casing, the strips and the re taining devices rigidly together.

In testimony whereof I affix my signature in presence of two witnesses.

NILS D. LEVIN.

Witnesses:

DUDLEY T. Frsmm, HARRY C. DEAN.

with faces of adjoining strips, 

